Catalytic composition and process for the alkylation or transalkylation of aromatic compounds

ABSTRACT

A catalytic composition is described for the alkylation or transalkylation of aromatic compounds consisting of zeolite Beta, as such or modified by the isomorphic substitution of aluminium with boron, iron or gallium or by the introduction of alkaline/earth-alkaline metals following ion exchange processes, and of an inorganic ligand, wherein the extrazeolite porosity, i.e. the porosity obtained by adding the mesoporosity and macroporosity fractions present in the catalytic composition itself, is such as to be composed for a fraction of at least 25% of pores with a radius higher than 100 Å.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to catalytic compositions consisting ofzeolite Beta (as such or modified) and a ligand which can be usedparticularly in processes for the alkylation of aromatic hydrocarbonswith olefins, in particular benzene with light olefins and morespecifically with ethylene to give ethylbenzene and with propylene togive cumene. The catalytic composition of the present invention is alsoparticularly suitable in the transalkylation of aromatic hydrocarbonswith polyalkylated aromatic hydrocarbons, especially of benzene withdiethylbenzene to give ethylbenzene and benzene with diisopropylbenzeneto give cumene.

2. Description of the Background

Former alkylation processes, still widely used in the petrolchemicalindustry for the production of the two organic intermediates quotedabove, involve the use of a catalyst based on phosphoric acid andinfusorial earth in a fixed bed for cumene and AlCl₃ in slurry forethylbenzene. The possibility of substituting these catalysts withnon-polluting, non-corrosive and regenerable materials such a zeoliticcatalysts has been known for some time.

There are mainly two types of problems however arising from the use ofzeolitic catalysts in alkylation reactions such as those listed above:

a higher percentage of polyalkylated by-products;

a more rapid deactivation of the zeolitic catalyst.

The first problem compels the use of a second reactor, if the alkylationstep is carried out at an insufficiently high temperature, forrecovering said by-products, mainly consisting of dialkylates, bytransalkylation with benzene, or their direct recycling into alkylationif instead this step is carried out at a sufficiently high temperature.

On the other hand, the second problem, a more rapid deactivation of thecatalyst, compels a certain frequency of necessary thermal regenerationswhich will be greater in number the shorter the duration of the singlereaction cycle intended as the duration of the catalyst between twosuccessive thermal regenerations. It is in fact evident that a greaterduration of the single reaction cycle will lead to a lower total numberof thermal regenerations, with the same complete duration of thecatalyst, and on the other hand this complete duration may in turndepend on the total number of thermal regenerations undergone by thecatalyst itself and can therefore increase with a greater duration ofthe single reaction cycle.

The increase in duration per single reaction cycle and consequently inthe productivity can be basically obtained by proceeding in twodirections:

by non-thermal regeneration techniques in situ as to allow for minimumshiftings or which may easily be accomplished with respect to normalrunning conditions in the reaction;

intervening on the catalyst.

Various patents claim processes and expedients in the first directionindicated; for example patent PCT/92/02877 describes a process forextending the duration of the single reaction cycle between two thermalregenerations for catalysts based on zeolites in alkylation reactions;this process basically consists in the continuous feeding of a moderateconcentration of H₂ O together with the reagents.

U.S. Pat. No. 5,518,897 discloses instead a process for reactivatingcatalysts based on zeolites in alkylation reactions by interruption ofthe olefin stream and substitution with a moderate stream of hydrogenunder certain conditions and for a certain period of time. This wouldenable the catalytic activity to be brought back to normal values andthus lengthen the duration of the single reaction cycle before thermalregeneration. As far as the second point is concerned, i.e. thepreparation of a catalyst with particular duration characteristics persingle reaction cycle, it is possible to cite for example U.S. Pat. No.4,870,222 which claims an alkylation and transalkylation process forproducing cumene with the use of an amorphous silica/alumina catalyst inalkylation and a second catalyst based on mordant in transalkylation.

The catalyst based on mordant bound with alumina used in transalkylationis subjected to a modification treatment of the porous structure inorder to obtain a higher Specific Surface Area value (SSA) equal to atleast 580 m² /g.

It is evident that the value is typical of the components zeolitemordant and alumina, used in the preparation of the catalyst and alsoobviously depends on the relative percentage actually present; thepatent cites an example relating to a material containing 10% of ligandand which after the treatment claimed increases the SSA from 540 m² /gto 620 m² /g. This treatment creates a greater activity of the catalystin transalkylation and also a longer duration as shown by the life testsdescribed in the examples of the patent.

SUMMARY OF THE INVENTION

We have found that in the case of catalysts prepared starting fromzeolite Beta and an inorganic ligand, used in alkylation reactions ofaromatics with light olefins, there is a surprising effect of the porousstructure of the catalyst, rather than its SSA, in particular of theporous structure not related to the microporosity itself of the Betazeolite and more specifically of the Pore Size Distribution of the meso-and macro-porous fractions present in the catalyst. The catalysts wehave found have certain porosity characteristics which guarantee highperformances in terms of duration and therefore productivity for eachreaction cycle, together with excellent mechanical characteristics suchas crushing strength and abrasion resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 are graphs showing pore size distribution for Catalysts A-D,in Examples 1-4, respectively.

FIG. 5 is a graph showing the conversion trend of propylene in relationto the time on stream for each of Catalysts A-D, in Examples 5-8,respectively.

FIG. 6 is a graph showing the conversion trend of ethylene in relationto the time on stream for each of Catalysts A-D, in Examples 9-12,respectively.

FIG. 7 is a graph showing the trend of the concentration of cumene inrelation to reaction time for Catalysts A and B in Examples 13 and 14,respectively.

DETAILED DESCRIPTION OF THE INVENTION

The catalytic composition of the present invention by the alkylation ofaromatic compounds, consists of:

zeolite Beta, as such or modified by the isomorphic substitution ofaluminium with boron, iron or gallium or modified by the introduction ofalkaline and/or earth-alkaline metals following ion-exchange processes;

an inorganic ligand preferably selected from silicon, aluminium,zirconium, magnesium oxides or natural clays or combinations of these,

and is characterized in that the extrazeolite porosity, i.e. theporosity obtained by adding the mesoporosity and macroporosity fractionspresent in the catalytic composition itself, (consequently excluding thecontribution of microporosity relating to the zeolite Beta), is such asto consist for a fraction of at least 25%, preferably at least 35%, ofpores with a radius higher than 100 Å.

The productivity and therefore duration per single reaction cycle isinfact more than double if the catalyst possesses this particularporosity which is the main characteristic of the present invention andthis effect is independent from the type of inorganic ligand used. Theporosity in the fraction with a radius which is greater than 450 Åshould preferably be less than 0.25 cc/g when the diameter of thecatalytic particles is less than or equal to 0.8 mm. The role of theporous structure claimed herein is evidently intended to reduce thedeactivation rate of the catalyst i.e. the rate of deposition of thecarbonious products formed during the reaction, responsible for thedeactivation.

It is clear from the following examples that there is probably a problemrelating to the diffusion of the reagents and products, a so-calledmorphological diffusion, through the porous structure of the catalyst inthe part non related to the zeolite, i.e. through the meso- andmacro-porosity fraction; in spite of the greater width of the pores thisfraction is in fact characterized by a lesser connectivity and greatertwisting with respect to the tridimensional, neat and open-endedchannels typical of the zeolite Beta which form the microporositypresent in the catalyst and inside which the catalytic activity takesplace.

This catalyst therefore has certain porosity characteristics whichguarantee high performance in terms of duration and consequentlyproductivity per single reaction cycle, together with excellentmechanical characteristics such as crushing strength and abrasionresistance.

Zeolite Beta, made known through U.S. Pat. No. 3,308,069, is asynthetic, crystalline, porous material having the composition

     (x/n)M(1+0.1-x)TEA!AlO.sub.2.ySiO.sub.2.wH.sub.2 O

wherein x is less than 1, y is between 5 and 100, w between 0 and 4, Mis a metal of the groups IA, IIA, IIIA or a transition metal and TEA istetraethylammonium.

The zeolite Beta used can be in any form (acid, partially acid orcontaining alkaline and/or earth-alkaline cations).

Modifications of zeolite Beta can be obtained by the partial or totalisomorphous substitution of aluminium with boron: patent BE-877205 forexample describes a porous crystalline boron-silicate called boralite-B,patent application EP-55046 describes an isomorphous zeolite withzeolite Beta in which the aluminium has been partially substituted withboron, iron or gallium; patent application IT-M193A001295 describes amodification by ionic exchange to introduce controlled quantities ofalkaline and/or earth-alkaline metals.

Zeolites Beta modified by the introduction of suitable quantities ofalkaline and/or earth-alkaline ions are prepared as described in U.S.Pat. No. 3,308,069, subsequent exchange with ammonium and calcination toobtain the zeolite Beta in a completely acid form, further exchange tointroduce calibrated quantities of an ion selected from Na⁺, K⁺ or Ca²⁺.The exchange is carried out using the known techniques, as described byR. P. Townsend in "Ion exchange in zeolites", Studies Surf.Scien.Cat.,vol. 58, pages 359-390, 1991. The sodium, potassium and calcium saltswhich can be used for the exchange are for example the correspondingacetates, nitrates and chlorides.

The catalyst is prepared starting from zeolite Beta and an inorganicligand by a process capable of creating a porosity which can bedetermined "a priori" and in accordance with the present invention.

The catalyst prepared starting from the above components has in fact arather extended porosity which can be basically defined as trimodal forthe contemporaneous presence of microporosity, mesoporosity andmacroporosity defined according to the Dubinin classification indicatedin Surface Area Determination-IUPAC-Proceedings of the InternationalSymposium on Surface Area Determination, Bristol U.K. 1969.

In particular the ranges of porosity which we refer to are thefollowing:

    ______________________________________                                        ∞ > radius pores Å > 1000                                                                 macroporosity                                           1000 > radius pores Å > 15                                                                      mesoporosity                                            15 > radius pores A   microporosity                                           ______________________________________                                    

The porosity of the catalyst depends in fact on both the components,which have only microporosity as far as zeolite Beta is concerned andgenerally mesoporosity as far as the inorganic ligand is concerned, andon the particular process used for producing the catalyst, necessary forits use in, for example, fixed-bed reactors.

The production process used by us has absolutely no influence on themicroporosity present in the catalyst, which obviously only depends onthe percentage of zeolite Beta present, but rather on the quantity ofmesoporosity and macroporosity, i.e. on the so-called extrazeolitefraction of porosity present in the catalyst.

The porosity of the catalyst is measured using two different techniquessuch as physical absorption of nitrogen at liquid nitrogen temperaturewith a Carlo Erba Sorptomatic 1990 instrument, and the intrusion ofmercury under pressure with a Carlo Erba Porosimeter 2000 instrument,basically following the indications contained in chapters 12 and 13 andchapter 20 of the volume Introduction to Powder Surface Area--Lowell,Seymour-Wiley Interscience publ. with respect to the analysisconditions.

The process used for forming the catalyst of the present invention canbe of any kind: the catalyst can in fact be prepared in the form ofpellets, bars, cylinders or any other form considered suitable for itsuse in alkylation reactions of aromatics with light olefins and inparticular with ethylene and propylene. The extrusion process ispreferably used, i.e. the production of the catalyst into smallcylinders called pellets.

The parameters actually used during the preparation of the catalyst intopellets are essential for controlling and obtaining the porositycharacteristics indicated above.

This control depends on several factors of which the most important areundoubtedly the extrusion back-pressure and particle size of the zeoliteBeta and inorganic ligand used.

With the same components the control of the extrusion back-pressure cantherefore be carried out by the modification of different variablestypical of an extrusion process including the type of machine used, therevolution speed of the compressing section, the diameter of the outputholes or nozzles of the extruded fresh product, the feeding humidity ofthe extruder, the quantity and quality of the peptizing agent possiblyused for the preparation of the feeding to the extruder and the presenceof particular substances suitable for giving plasticity and flowabilitycharacteristics during extrusion.

What remains important however is the definite possibility of preciselydetermining the porous structure of the catalyst within the extrazeoliterange of porosity, i.e. which can not be attributed to the quantity andquality of the percentage of zeolite present in the catalyst, bycontrolling the above variables.

Experts in production processes of catalysts and in particular expertsin extrusion certainly know the effect, contribution and role of theabove variables in determining the porous structure of a catalystprepared in this way and can therefore reproduce without difficultiesthe characteristics of the catalytic composition claimed herein.

The catalytic composition of the present invention is particularlysuitable in alkylation processes of aromatics with light olefins andparticularly benzene with ethylene to give ethylbenzene and withpropylene to give cumene.

The alkylation reaction can be industrially carried out on a continuous,semi-continuous and batch scale, and in a gas, liquid or mixed phase;the catalyst can be contained in one or more catalyst beds inside thereactor and the system can contain several reactors in series.

The feeding of the olefin can be more or less distributed along thereactor or between several catalyst beds in order to minimize thepolyalkylation reactions of the aromatic substrate and in suchquantities as to have a molar ratio Aromatic!/ Olefin! preferably ofbetween 1 and 20, even more preferably between 2 and 8. The reactiontemperature is between 100° C. and 300° C., preferably between 120° C.and 230° C.; the pressure is between 10 atm and 50 atm, preferablybetween 20 atm and 45 atm; the WHSV space velocity is between 0.1 and200 h⁻¹, preferably between 1 and 10 h⁻¹.

It should be noted however that the combination of temperature andpressure conditions actually used must be such as to guarantee that thealkylation reaction basically takes place in the liquid phase.

Using the catalytic composition of the present invention in alkylationprocesses, a longer life and productivity of the catalyst can beobtained per single reaction cycle with respect to the materialsprepared not according to the present invention.

This result is undoubtedly due to the particular pore distribution whichis the fundamental characteristic of the catalyst of the presentinvention.

More specifically, as can be clearly seen in the examples below, thevariation of parameters relating to the porous structure in thecatalysts of the present invention compared to materials not inaccordance with this, after an accelerated catalytic test with partialdeactivation of the catalyst, is in fact qualitatively andquantitatively different.

This variation can naturally be clearly observed from the directmeasurement of the fractions of micro-, meso- and macro-porosity in thecatalysts after the catalytic test. The variations can be even moreclearly noted after determining the SSA parameter (Specific SurfaceArea) in the fresh and deactivated catalysts. The determination of theSSA on fresh catalysts and following the catalytic test, described inthe examples below, is carried out by physical nitrogen adsorption asdescribed above and processing the experimental isotherm data obtainedaccording to the BET theory.

The BET theory is an extension of the Langmuir theory for multistratephysical adsorption and can be successfully applied in the interpolationof adsorption isotherms of the type I,II and IV (according to theBrunauer, Deming and Teller classification) as indicated by S. Brunauer,P. H. Emmet and E. Teller, J.Amer.Soc., 60,309(1938) and in S. J. Gregg,K. S. W. Sing, Adsorption, Surface Area and Porosity, Academic PressLondon 2nd ed.(1982).

The catalytic compositions of the present invention and generally allmaterials containing not a low percentage of component havingmicroporosity generate a physical adsorption isotherm with type Icharacteristics (typical of microporous materials) however associatedwith type IV isotherm characteristics (typical of mesoporous materials)if there is a mesoporosity component.

In this case the SSA determination using the BET theory compels the useof the particular form of the so-called 3 parameter equation, i.e. notlinear (H. Reichert, Diplomarbeit, Joh.Gutenberg Universitat, Mainz1988). The interpolation of the physical adsorption experimentalisotherm provides Vm (monolayer volume) values, necessary forcalculating the SSA, C(BET) and N(M. Avriel, Nonlinear Programming,Prentice Hall, 224 (1976).

As a consequence of the physical meaning which the BET theory assigns tothe C(BET) and N parameters it can be observed that the C(BET) parameterdecreases as the microporosity character decreases whereas the Nparameter increases and these parameters can therefore be considered asindexes of the content or residual character of microporosity of thematerials being examined.

In all the materials prepared it can in fact be noted that the variationof the above parameters is in the sense indicated by the catalytic testand deactivation, considering that microporosity is the fraction ofporosity of the catalyst inside which the catalytic activity mainlytakes place, these parameters are particularly useful for following theobserved variation due by the same microporous fraction in the catalystafter the catalytic test.

The direct measuring of the fraction of microporosity as specified aboveis carried out by physical nitrogen adsorption and by the t-plot madeaccording to de Boer (B. C. Lippens and J. H. de Boer, J.Catalysis,4,319, 1965).

The catalytic compositions of the present invention have in fact adifferent variation of these parameters and micorporosity content afterdeactivation compared to those not in accordance with the presentinvention. In practice analysis of the porous structure of thedeactivated materials after the catalytic tests described in thefollowing examples shows that the greater productivity and longer lifein alkylation reactions with olefins are accompanied by a greater lossof microporosity, i.e. of the porosity responsible for the catalyticactivity, in the catalytic compositions claimed herein.

The materials which are not in accordance with the present invention andtherefore having a lower productivity and shorter life, show, afterdeactivation, an even higher microporosity content which is evidentlyhowever no longer accessible for obtaining the catalytic activity.

In practice the presence of a fraction of porosity which is higher than100 Å in radius, equal to at least 25% of the extrazeolite porosity inthe fresh catalyst, guarantees a lower deactivation rate owing to agreater use of the microporous fraction of the catalyst, i.e. of thefraction responsible for the catalytic activity during alkylationreactions of benzene with olefins.

The catalytic composition of the present invention is also particularlysuitable in the transalkylation processes of aromatic hydrocarbons withpolyalkylated aromatic hydrocarbons. The aromatic hydrocarbon can beselected from benzene, toluene, ethylbenzene and xylene and preferablybenzene.

The polyalkylated aromatic hydrocarbon is preferably selected fromdiethylbenzene and diisopropylbenzene. The transalkylation of benzenewith diethylbenzene to give ethylbenzene and benzene withdiisopropylbenzene to give cumene are particularly preferred.

The transalkylation reaction must be carried out under such conditionsas to take place at least partially in the liquid phase. It ispreferably carried out at a temperature of between 100° and 350° C., ata pressure of between 10 and 50 atms and at a WHSV of between 0.1 and200 hours⁻¹. Even more preferably, the temperature is between 150° C.and 300° C., the pressure is between 20 and 45 atms and the WHSV isbetween 0.1 and 10 hours⁻¹. The molar ratio between aromatic hydrocarbonand polyalkylated aromatic hydrocarbon can vary between 1 and 30.

According to a preferred aspect of the present invention thepolyalkylated aromatic hydrocarbon prevalently or totally consists ofdiisopropylbenzene or prevalently or totally consists of diethylbenzene.For example the fraction "cumene bottoms" produced in akylationprocesses to give cumene can be used as polyalkylated aromatichydrocarbon prevalently consisting of diisopropylbenzene.

The following examples provide a better illustration of the presentinvention but do not limit it in any way.

EXAMPLES Preparation of the Zeolite Beta Used in the Examples

58.8 g of tetraammonium hydroxide at 40% by weight in an aqueoussolution and 1.9 g of sodium aluminate are added to 58.4 g ofdemineralized water. The mixture is heated to about 80° C. and is leftunder stirring until complete dissolution. The limpid solution thusobtained is added to 37.5 g of Ludox HS colloidal silica at 40% byweight. A homogeneous suspension is obtained having pH 14, which ischarged into a steel autoclave and left to crystallize underhydrothermal conditions at 150° C. for 10 days, under static conditionsand at autogenous pressure. The crystallized product is separated byfiltration, washed, dried for 1 hour at 120° C., calcinated for 5 hoursat 550° C. and ion-exchanged into acid form by treatment with ammoniumacetate and subsequent calcination.

The sample thus obtained, upon chemical analysis, has the followingcomposition expressed as a molar ratio:

    SiO.sub.2 /Al.sub.2 O.sub.3 =19.3

The product was characterized by power X-ray diffraction.

Example 1

A catalyst called CATALYST A is prepared, based on zeolite Beta (whosepreparation is described above) and alumina following an extrusionprocess whose main parameters effectively used are indicated in Table Itogether with the relative porosity values of the end catalyst.

The extrusion parameters indicated in Table I guarantee the productionof a material with the particular Pore Size Distribution claimed hereinand shown in FIG. 1 for the catalyst prepared as described above (FIG. 1also indicates in ordinate the cumulative volume in cc/g and thepercentage (%) of said volume and in abscissa the pore radius in Å).

As can be seen from FIG. 1 there are basically two fractions presentwithin the porosity indicated by the porosimeter (>37 Å) and i.e. thefraction up to 100 Å of radius and the higher one; the second is in factpredominant and falls into the particular Pore Size Distributionclaimed.

Example 2--Comparative

A catalyst called CATALYST B is prepared using the same components asexample 1 but substantially modifying the extrusion process and usingthe parameters described in Table II which also indicates the dataconcerning the porosity of the end catalyst.

FIG. 2 shows the Pore Size Distribution obtained from the porosimeterfrom which it can be noted that the greater part of extrazeoliteporosity consists of pores with a radius of less than 100 Å.

Example 3

A catalyst called CATALYST C is prepared using the same components asexample 1 but substantially modifying the extrusion process and usingthe parameters described in Table III which also indicates the dataconcerning the porosity of the end catalyst.

FIG. 3 shows the Pore Size Distribution obtained from the porosimeterfrom which it can be noted that the greater part of extrazeoliteporosity consists of pores with a radius higher than 100 Å.

Example 4

A catalyst called CATALYST D is prepared substantially modifying theextrusion process as indicated in table IV and using silica/alumina asinorganic ligand. FIG. 4 shows the Pore Size Distribution obtained fromthe porosimeter from which it can be noted that the greater part ofextrazeolite porosity consists of pores with a radius higher than 100 Å.

Example 5

An alkylation test of benzene with propylene is carried out using anexperimental device consisting of a micropilot catalyst fixed-bedreactor made of Inconel 600 with an internal diameter of 2 cm and totallength of 80 cm, feeding tanks for benzene and propylene, dosage pumpsfor the separate feeding of the two reagents in the liquid phase,temperature and pressure control, automatic discharge of the effluentfrom the reactor and automatic sampling system of the feeding andeffluent from the reactor for continuous analysis of the reagents andproducts.

This analysis is carried out with an HP 5890 gas-chromatograph connectedto a processor, carrier gas He, steel column of 1/8"×1.5 mt packed withFFAP 15% on Chromosorb W-AW, injector temperature 250° C., Temperatureprogrammed from 50° to 220° C., detector temperature 250° C. and TCDdetector for feeding to the reactor.

The reactor effluent is analyzed with a DANI 8520 gas-chromatographconnected to a processor, carrier gas He, capillary column in moltensilica with an internal diameter of 0.2 mm length of 50 mt and eluatingliquid methylsilicon 0.5 micron, injector temperature 250° C.,temperature programmed from 40° to 240° C., detector temperature 250° C.and FID detector.

The reaction conditions used during the test are the following:

Inlet T=150° C.

P=30 bar

WHSV=5.5 hr⁻¹

Benzene!/ Propylene!=5.7

4.5 g of catalyst prepared as described in example 1 (CATALYST A) and11.5 of inert material are then charged.

FIG. 5 shows the conversion trend of propylene in the ordinate (%) inrelation to the "time on stream" in hours (hr) in the abscissa obtainedusing a bench reactor.

As can be seen from FIG. 5 the conversion of propylene at the end of thetest was equal to about 27% after 307 continuous running hours withoutany modification of the above reaction conditions.

Table V shows the data relating to the porosity of the catalyst at theend of said test.

As can be noted from comparing the values of table V with thoseindicated for the fresh catalyst in table I, there has been a total dropin porosity mainly on the part of the microporous fraction.

This can also be observed from parameters "C" and "N" obtained by BETprocessing whose variation is a definite indication of the decrease inthe microporosity.

Example 6--Comparative

The catalyst prepared as described in example 2 (CATALYST B) is chargedunder the same conditions as example 5.

The conversion trend of the propylene during the test in relation to thetime on stream is shown in FIG. 5. As can be seen in FIG. 5 theconversion of propylene at the end of the test was equal to about 19%after only 144 continuous running hours without any modification of theabove reaction conditions.

Table VI shows the data relating to the porosity of the catalyst at theend of this test.

As can be seen from comparing the values of table VI with thoseindicated for the fresh catalyst in table II, there has been a totaldrop in porosity mainly on the part of the mesoporous fraction i.e. thefraction of porosity other than the micropores present in the catalyst.

Unlike the results obtained in the previous example it can be observedthat also when the productivity is less than half with respect to theprevious example the microporous fraction where the catalytic activityoccurs is still mainly free but evidently not accessible to the reagentsas can be seen from observing the data shown in FIG. 5.

On the other hand the conservation of a greater microporosity, withrespect to the previous example for this material after the catalytictest, is perfectly clear from observing parameters "C" and "N" whosevariation is in fact considerably different and to a lesser extentcompared with the material of the previous example.

It is therefore evident that this catalyst, which is not in accordancewith the present invention, is characterized by a greater deactivationrate with respect to the material relating to the present invention andprepared as described in example 1.

Example 7

The catalyst prepared as described in example 3 (CATALYST C) is chargedunder the same conditions as example 5.

The conversion trend of the propylene during the test in relation to thetime on stream is shown in FIG. 5. As can be seen from FIG. 5 theconversion of propylene at the end of the test was equal to about 30%after 300 hours of continuous running without any modification of theabove reaction conditions.

It is clear that the performances of the catalyst can be perfectlycompared, with respect to the life and consequently productivity of thecatalyst, with those obtained using the material prepared according toexample 1.

Example 8

The catalyst prepared as described in example 4 (CATALYST D) is chargedunder the same conditions as example 5.

The conversion trend of the propylene during the test in relation to thetime on stream is shown in FIG. 5. As can be seen from FIG. 5 theconversion of propylene at the end of the test was equal to about 30%after 300 hours of continuous running without any modification of theabove reaction conditions.

It is clear that the performances of the catalyst can be perfectlycompared, with respect to the life and consequently productivity of thecatalyst, with those obtained using the material prepared according toexample 1.

Example 9

An alkylation test of benzene with ethylene is carried out in a stirredbatch reactor, charging the catalyst, the aromatic andsubsequently--when the following temperature conditions have beenreached--the quantity of ethylene necessary for obtaining the molarratio between the reagents specified below.

Temp.=180° C.

Pressure=45 bar

Benzene charged=400 cc

C6!/ C2!=4.4

Catalyst=1.7 g

During the test samples of the reaction liquid are taken in suchquantities as not to greatly modify the total reaction volume andanalyzed by gas-chromatography with a Perkin-Elmer instrument, PTVinjector on column, temperature programmed from 80° to 240° C.,wide-bore methylsilicon capillary column and FID detector. The catalystused is that prepared according to example 1 (CATALYST A).

FIG. 6 shows the conversion trend of the ethylene in the ordinate (%) inrelation to the time on stream in hours (hr) in the abscissa using astirred batch reactor.

Example 10--Comparative

A test is carried out under the conditions described in example 9 butusing the catalyst prepared as described in example 2 (CATALYST B).

The conversion trend of the ethylene in relation to the reaction time isshown in FIG. 6.

From the inclination of the curve a lower reaction rate can be observedwith respect to the previous example and a curve trend which indicates adeactivation of the catalyst with a reaction rate close to zero withouta quantitative conversion of the ethylene.

Example 11

A test is carried out under the conditions described in example 9 butusing the catalyst prepared as described in example 3 (CATALYST C).

The conversion trend of the ethylene in relation to the reaction time isshown in FIG. 6.

The behaviour of the catalyst is basically similar to that of thematerial of example 1.

Example 12

A test is carried out under the conditions described in example 9 butusing the catalyst prepared as described in example 4 (CATALYST D).

The conversion trend of the ethylene in relation to the reaction time isshown in FIG. 6.

The behaviour of the catalyst is basically similar to that of thematerial of example 1.

                  TABLE I                                                         ______________________________________                                        CATALYST A                                                                    EXTRUSION PARAMETERS                                                          ______________________________________                                        Binder content     50 wt %                                                    Acid added         acetic                                                     Acid added/binder  0.034 wt/wt                                                Extrusion pressure 40-50 bar                                                  Pellet: diameter/height                                                                          2 mm/10 mm                                                 CATALYST                                                                      SSA (BET 3 par.)   460 m.sup.2 /g (506 m.sup.2 /g DR*)                        "C" parameter (BET 3 par)                                                                        1.977                                                      "N" parameter (BET 3 par)                                                                        2.6                                                        Total pore volume  0.52 cc/g                                                  Macropore volume  A!                                                                             0.01 cc/g                                                  Mesopore volume  B!                                                                              0.39 cc/g                                                  Pore vol. with radius >100A  C!                                                                  0.25 cc/g                                                  |  C!/( A! +  B!)                                                                       62%                                                        Micropore volume   0.12 cc/g                                                  Crushing strength along diameter                                                                 31 Kg                                                      ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        CATALYST B                                                                    EXTRUSION PARAMETERS                                                          ______________________________________                                        Binder content     50 wt %                                                    Acid added         acetic                                                     Acid added/binder  0.049 wt/wt                                                Extrusion pressure 220-240 bar                                                Pellet: diameter/height                                                                          2 mm/10 mm                                                 CATALYST                                                                      SSA (BET 3 par.)   433 m.sup.2 /g (476 m.sup.2 /g DR*)                        "C" parameter (BET 3 par)                                                                        2.181                                                      "N" parameter (BET 3 par)                                                                        2.7                                                        Total pore volume  0.43 cc/g                                                  Macropore volume  A!                                                                             0.00 cc/g                                                  Mesopore volume  B!                                                                              0.31 cc/g                                                  Pore vol. with radius >100A  C!                                                                  0.07 cc/g                                                  |  C!/( A! +  B!)                                                                       23%                                                        Micropore volume   0.12 cc/g                                                  Crushing strength along diameter                                                                 34 Kg                                                      ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        CATALYST C                                                                    EXTRUSION PARAMETERS                                                          ______________________________________                                        Binder content     50 wt %                                                    Acid added         acetic                                                     Acid added/binder  0.038 wt/wt                                                Extrusion pressure 4-6 bar                                                    Pellet: diameter/height                                                                          2 mm/10 mm                                                 CATALYST                                                                      SSA (BET 3 par.)   458 m.sup.2 /g (492 m.sup.2 /g DR*)                        "C" parameter (BET 3 par)                                                                        1.960                                                      "N" parameter (BET 3 par)                                                                        2.5                                                        Total pore volume  0.81 cc/g                                                  Macropore volume  A!                                                                             0.14 cc/g                                                  Mesopore volume  B!                                                                              0.55 cc/g                                                  Pore vol. with radius >100A  C!                                                                  0.40 cc/g                                                  {  C!/( A! +  B!}  58%                                                        Micropore volume   0.12 cc/g                                                  Crushing strength along diameter                                                                 7 Kg                                                       ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                        CATALYST D                                                                    EXTRUSION PARAMETERS                                                          ______________________________________                                        Binder content     50 wt %                                                    Acid added         acetic                                                     Acid added/binder  0.047 wt/wt                                                Extrusion pressure 20-30 bar                                                  Pellet: diameter/height                                                                          2 mm/10 mm                                                 CATALYST                                                                      SSA (BET 3 par.)   506 m.sup.2 /g (556 m.sup.2 /g DR*)                        "C" parameter (BET 3 par)                                                                        1.187                                                      "N" parameter (BET 3 par)                                                                        2.7                                                        Total pore volume  0.84 cc/g                                                  Macropore volume  A!                                                                             0.28 cc/g                                                  Mesopore volume  B!                                                                              0.44 cc/g                                                  Pore vol. with radius >100A  C!                                                                  0.51 cc/g                                                  |  C!/( A! +  B!)                                                                       71%                                                        Micropore volume   0.12 cc/g                                                  Crushing strength along diameter                                                                 19 Kg                                                      ______________________________________                                    

                  TABLE V                                                         ______________________________________                                        CATALYST A (after alkylation test)                                            CATALYST                                                                      ______________________________________                                        SSA (BET 3 par.)   242 m.sup.2 /g (248 m.sup.2 /g DR*)                        "C" parameter (BET 3 par)                                                                        135                                                        "N" parameter (BET 3 par)                                                                        5.6                                                        Total pore volume  0.40 cc/g                                                  Macropore volume  A!                                                                             0.01 cc/g                                                  Mesopore volume  B!                                                                              0.34 cc/g                                                  Micropore volume   0.05 cc/g                                                  ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                        CATALYST B (after alkylation test)                                            CATALYST                                                                      ______________________________________                                        SSA (BET 3 par.)   287 m.sup.2 /g (316 m.sup.2 /g DR*)                        "C" parameter (BET 3 par)                                                                        489                                                        "N" parameter (BET 3 par)                                                                        3.9                                                        Total pore volume  0.37 cc/g                                                  Macropore volume  A!                                                                             0.00 cc/g                                                  Mesopore volume  B!                                                                              0.27 cc/g                                                  Micropore volume   0.10 cc/g                                                  ______________________________________                                         DR* = Dubinin Radushkevich Method                                        

Example 13

A transalkylation test of benzene is carried out with a mixture, whosecomposition is indicated in the following table, which simulates atypical composition of "cumene bottoms".

                  TABLE VII                                                       ______________________________________                                        "Cumene bottoms"                                                                            % (w/w)   Reaction condition                                    ______________________________________                                        Cumene        5.2       temp. = 200° C.                                N-propylbenzene                                                                             130 ppm   Press. = 30 bar                                       Phenyl-C4     0.5       benzene = 250 g                                       Phenyl-C5     0.8       Cumene bottoms = 90 g                                 m,o,p diisopropylbz                                                                         73.6      Catalalyst = 3.5 g                                    Heavies       19.8                                                            ______________________________________                                    

The catalyst is that prepared according to example 1 (CATALYST A) and isplaced inside appropriate rotating baskets with a rotation rate equal to800 rpm. The transalkylation test is carried out by charging into astirred autoclave, the catalyst, the benzene and subsequently, when thetemperature conditions indicated in table VII above have been reached,the mixture of "cumene bottoms".

FIG. 7 shows the trend of the concentration of cumene (%) in theordinates in relation to the reaction time expressed in hours, in theabscissa (CATALYST A CURVE). The analysis of the liquid sample iscarried out using the equipment and conditions described in example 9.

Example 14--Comparative

A test is carried out under the same conditions described in example 13but using the catalyst prepared as described in example 2 (CATALYST B).

The trend of the concentration of Cumene in relation to the reactiontime is shown in FIG. 7 (CATALYST B CURVE).

From the gradient of the curve a lower reaction rate can be observedwith respect to the curve obtained in example 13 together with atendency to reach a plateau which indicates a more rapid deactivation ofthe catalyst.

We claim:
 1. Catalytic composition comprising zeolite Beta or modifiedzeolite Beta, and an inorganic binder selected from the group consistingof aluminum oxide, magnesium oxide, natural clays, and mixtures thereof,wherein at least 25% of the pore volume obtained by adding the fractionsof mesoporosity and macroporosity present in the catalytic compositionitself consists of pores with a radius higher than 100 Å, and whereinthe porosity in the fraction with a radius which is greater than 450 Åis less than 0.25 cc/g when the diameter of the catalytic particles isless than or equal to 0.8 mm.
 2. Catalytic composition according toclaim 1 wherein the porosity obtained by adding the fractions ofmesoporosity and macroporosity present in the catalytic compositionitself, is at least 35% of pore volume with a radius higher than 100 Å.3. Catalytic composition according to claim 1 wherein the bindercomprises alumina.
 4. Process for the alkylation of aromatic compoundscomprising putting said compounds in contact with a light olefin in thepresence of a catalytic composition in accordance with any one of claims1 or 2, operating at a temperature of between 100° and 300° C. and apressure of between 10 and 50 atm and a WHSV space velocity of between0.1 and 200 h⁻¹.
 5. Process according to claim 4 wherein the temperatureis between 120° and 230° C., the pressure between 20 and 45 atm and theWHSV space velocity between 1 and 10 h⁻¹.
 6. Process according to claim4 wherein the molar ratio between aromatic compound and olefin isbetween 1 and
 20. 7. Process according to claim 4 wherein the molarratio between aromatic compound and olefin is between 2 and
 8. 8.Process for the transalkylation of an aromatic hydrocarbon whichcomprises putting the aromatic hydrocarbon in contact with apolyalkylated aromatic hydrocarbon under at least partial liquid phaseconditions in the presence of a catalytic composition according to anyone of claims 1 or
 2. 9. Process according to claim 8 carried out at atemperature of between 100° and 350° C., at a pressure of between 10 and50 atms and at a WHSV of between 0.1 and 200 hours⁻¹.
 10. Process inaccordance with claim 9 carried out at a temperature of between 150° and300° C., at a pressure of between 20 and 45 atms and at a WHSV ofbetween 0.1 and 10 hours⁻¹.
 11. Process according to claim 8 wherein themolar ratio betwen the aromatic hydrocarbon and polyalkylated aromatichydrocarbon is between 1 and
 30. 12. Process according to claim 8wherein the aromatic hydrocarbon is selected from benzene, toluene,ethylbenzene and xylene.
 13. Process according to claim 12 wherein thearomatic hydrocarbon is benzene.
 14. Process according to claim 8wherein the polyalkylated aromatic hydrocarbon is selected fromdiethylbenzene and diisopropylbenzene.
 15. Process according to claim 8wherein the aromatic hydrocarbon is benzene and the polyalkylatedaromatic hydrocarbon is diethylbenzene.
 16. Process according to claim 8wherein the aromatic hydrocarbon is benzene and the polyalkylatedaromatic hydrocarbon is diisopropylbenzene.